There's nothing like a good-old brutal argument about the use of conjunctions (things like and, but or so). Most people are on one side or the other and they will not be moved. After all, a debate with anyone who passionately believes they are right will prove that conjunction opinion is a life-long thing: they either think that conjunctions should only ever be used to join words in sentences, or that people should relax and writers should be able to use them however they damn well like.
SEO copywriting: how can we use conjunctions?
The fact, whichever side of the debate you're on, is that there is no absolute rule on this which any of us have to actually stick to. Nowhere can you find a solid piece of literature by any authority of English language which can categorically prove that starting a sentence with and or but is wrong. A quick Google search will show you that, ever since language was invented, people have started their sentences with and or but. The only real rule is that when you're using conjunctions, you should probably think about the general guidelines, so that whatever you are writing doesn't sound crap. One of those guidelines is that you should consider using them to join parts of a sentence and consider starting a sentence in the more conventional way. That doesn't mean that anything else is off limits, of course. In fact, far from it.
Doing what feels right – the key to quality copywriting
Personally, where SEO copywriting is concerned – and fiction, and anything else, for that matter – I'm a fan of writing in a way that feels right. Conversational language works well for a reason: we all use it, and in our day-to-day lives, we never stop to consider if we should start our dialogue with conjunctions or not. The point, I think, is this: sometimes, starting a sentence with a conjunction does feel right. The world is full of rules which we all disobey and pay no attention to, yet somehow the notion that a conjunction must only be used to join words in a sentence has brainwashed millions of people all over the world, caused fights between academics (no, you can't) and creatives (yes, you can!) for centuries. Can you imagine a world where nobody dared to cross the road unless they were at a zebra crossing or a set of traffic lights? Just like it makes no sense to walk a mile down an empty road in order to cross where it is perfectly legal according to the law, it also makes no sense to obey ridiculous rules that merely hold us back from making a literary point.
The message matters more than anything
Besides all that, what us lovers of free conjunction usage keep reminding people is that SEO copywriting – like any form of copywriting – is all about the message. Sometimes, beginning a sentence with and or but divides two thoughts up nicely, or just keeps the flow. Really, if it's good enough for countless authors throughout time, what's the problem?
That's not to say that you shouldn't listen to your customer. You should. Always, every time. In SEO copywriting, the customer should always get what they asked for. And if they say no conjunctions at the start of sentences, fair enough. It's their copy.